1. Field of the Invention
The present invention relates to a communication apparatus and a communication method thereof.
2. Description of the Related Art
As is conventionally done in places such as conference rooms, screen information of an information terminal such as a personal computer (PC) is projected on a screen by using a projector, and thereby, information is shared among participants present. In many cases, the information terminal is connected by wire to the projector. In those cases, the information terminal is connected by a cable to an image input/output terminal (such as a digital visual interface (DVI) terminal) provided on the projector, and images are projected on the screen while the information terminal is operated in a position within reach of the cable.
When projectors are used in conferences or the like in comparatively spacious places, there are increasing cases in which a plurality of projectors are used and the conference is conducted with more pieces of information displayed by displaying different pieces of information with these projectors. There are also increasing cases in which a video conference system or the like uses screen projection with realistic sensation, for example, by using three large screens. In these cases, three projectors need to be prepared. For example, a horizontally long video image is divided into three video images, which in turn are projected by using the three projectors onto the three screens arranged adjacent to each other.
In the case of displaying video images different from each other with a plurality of projectors, it is conceivable to make the projectors project a plurality of pieces of screen information provided from a plurality of video image transmission sources (such as PCs). It is also conceivable to display the screen information provided from one PC with the three projectors. For example, three display connection ports are provided on the PC, and the three pieces of screen information are output from the three corresponding display connection ports.
In addition, the communication speed of wireless communication has increased in recent years, and it is already known that techniques to achieve wireless connections between projectors and information terminals are in practical use.
Japanese Patent Application Laid-open No. 2006-284990 discloses an image transmission multi-display system in which image data is divided in accordance with positions of a plurality of projectors, and each divided piece of image data positional information is associated with identification information of each of the projectors, so that image data to be sent is sent only to the projector corresponding thereto via a network. According to Japanese Patent Application Laid-open No. 2006-284990, an image divided into a plurality of pieces and sent by wireless transmission can be synthesized on a large screen by using a plurality of projectors.
In conventional methods of wireless connection, a wireless transmitter and a receiver have a one-to-one relation with each other. Therefore, in the case in which the different pieces of information are sent from one PC to three projectors, the information needs to be sent in a serial manner to the three projectors. In this case, the transmission capacity to each of the three projectors is one third of a transmission capacity of the transmission from the PC. Supposing that the PC sends the video data at a transmission rate of 30 frames per second (fps), the transmission rate for each one of the projectors is 10 fps, and thus, it is difficult to send an animation video image.
It is accordingly conceivable to send the video image using a plurality of channels that can transmit data independently from each other. For example, three of such channels are simultaneously used, and each of the channels sends the video data in parallel with each other. In this case, each of the three projectors is assigned with each one of the channels, and thereby, the transmission rate of 30 fps can be ensured for each of the projectors, thus making it possible to deal with the animation video image.
However, even when a plurality of channels are used, there are cases in which transmission channels between some of the projectors and the video image transmission source have a bad quality. For example, the quality of the transmission channels can deteriorate due to various factors such as that the distance between the video image transmission source (PC) and one of the projectors is long, that one of the projectors is in over-the-horizon communication for the video image transmission source, and that multipath fading occurs.
Therefore, there is a need for a communication apparatus and a communication method that suppress degradation in quality of communication in a particular receiver when the communication is performed from the communication apparatus to a plurality of receivers.